Process for upgrading green coffee

ABSTRACT

An improved process for upgrading green coffee by contacting green coffee with water and subjecting the mixture to elevated temperatures under pressure has been discovered. The key to the present invention is to control the moisture content of the green coffee and the steam pressure contacting the coffee, thus avoiding undue expansion of the coffee bean by introducing coffee and water into a vessel pressurized by steam such that expansion is inhibited during the treatment. Expansion of the beans on discharge from the pressure vessel is also minimized by avoiding a sudden release of pressure when the beans are discharged from the vessel.

Ponzoni et al.

' Filed:

PROCESS FOR UPGRADING GREEN COFFEE Inventors: George B. Ponzoni, SpringValley,

N.Y.; Michael G. Protomastro,

Woodridge; Arthur Stefanucci, Clifton, both of NJ.

Assignee: General Foods Corporation, White Plains, NY.

Sept. 28, 1971 Appl. No.2 184,586

Related U.S. Application Data Continuation-in-part of Ser. No. 90,198,Sept. 30, 1970, abandoned, which is a continuation-in-part of Ser. No.835,234, June 20, 1969, abandoned.

Adler et al 99/68 2,833,653 5/1958 Chase et al. 99/68 X 2,712,501 7/1955Hale et al. 99/68 X 3,106,470 10/1963 Spotholz 99/68 3,088,825 5/1963Todalian et al 99/68 Primary Examiner-Frank W. Lutter AssistantExaminer-William L. Mentlik Attorney-Bruno P. Struzzi et al.

[57] ABSTRACT An improved process for upgrading green coffee bycontacting green coffee with water and subjecting the mixture toelevated temperatures under pressure has been discovered. The key to thepresent invention is to control the moisture content of the green coffeeand the steam pressure contacting the coffee, thus avoiding undueexpansion of the coffee bean by introducing coffee and water into avessel pressurized by steam such that expansion is inhibited during thetreatment. Expansion of the beans on discharge from the pressure vesselis also minimized by avoiding a sudden release of pressure when thebeans are discharged from the vessel.

10 Claims, No Drawings BACKGROUND OF THE INVENTION This inventionconcerns a method for improving the quality of green coffee withcharacteristically high levels of undesirable flavor and aromaconstituents. It is well known that certain varieties of coffees such asRobustas have objectionable tarry, earthy, and bitter flavoinotesandthese undesirable characteristics have been associated with a high levelof undesirable volatiles.

There are many'processes shown in the prior art for stripping volatilematerials from coffee. Most of these utilize a vacuumsteaming-procedure. One prior art process described in U.S. Pat. No.2,278,473 by Albert Musher treats green or roasted coffee at moisturecontents below 20 or 25 percent under pressure at elevated temperaturesto produce an enhanced coffee bean. In Mushers'process the coffee beansare suddenly released from the pressure vessel to obtain an explodedstructure. Musher teaches that moisture content is controlled to insurethere is not too much moisture in the bean to enable the requiredexplosion.

Recently issued patents including French Pat. No. 2,002,189 publishedJuly 31, 1970 and assigned to Procter & Gamble, and U.S. Pat. No.3,572,235 issued Mar. 23, 1971 and assigned to Hills Brothers, teachsteam treating coffee under pressure at moisture contents up to 35percent water and 18 percent water, respectively, to upgrade the coffeeflavor. Two earlier U.S. Pats. No., assigned to. General Foods, Nos.3,088,825 and 3,'l06,470, teach steam pressure roasting of green coffeeto develop roasted beans of unusually high soluble solids content.

While some improvement in the flavor characteristics may be achieved viathe prior art processes, the present invention of overtly adding waterto green coffee and then steaming the mixture under specific pressureconditions has been found to produce additional upgrading in the flavorof low cost coffees such as Robustas and certain Brazilian coffees.

SUMMARY OF THE INVENTION Certain low-grade coffee characterized ashaving tarry, moldy, dirty, and earthy notes is contacted with water andtreated in a confined pressure vessel at elevated temperatures in orderto upgrade the flavor characteristics of the coffee. Unexpectedly,addition of water to the beans and treatment of the wet coffee withsteam to produce a final green coffee having an as is moisture contentof above 35 percent by weight water yields beverages after roasting withmore desirable characteristics. Water may be added before, during, orafter charging green coffee to the treatment vessel, the only criticalfactor being thatv an amount of water is added sufficient to insure thatthe treated coffee discharging from the vessel has a moisture content ofbetween above 35 percent and preferably from 40-50 percent water on anas is basis.

DESCRIPTION OF THE PREFERRED EMBODIMENT Green coffee is mixed with waterin a pressure lock and fed into a continuous pressure digester which ismaintained at a pressure of about 50-140 p.s.i., preferably by theaddition of steam. The coffee and water mixture is instantaneouslyexposed to high steam pressure and the water is drawn into the greencoffee, rapidly increasing the coffees moisture content. The coffee isconveyed through the digester is about l-l minutes, preferably about 5minutes or less, say from l-S minutes, and is discharged via a pressurelock wherein vapors are vented off such that the beans on discharge fromthe lock are essentially at atmospheric pressure. It is necessary toexpose the water moistened green coffee to a steam treatment underpressure in order to enable steam to penetrate throughout the coffee andaffecting volatile flavor materials in the green coffee bean and itsporosity, such that on discharge from the.

- vessel followed by subsequent roasting, the flavor of the finishedroasted coffee is improved. One method of obtaining the steam is tovolatilize some of the water introduced into the digester by applyingheat externally to the digester through a heating jacket or the like.

. Preferably, the coffee and water mixture is treated by introducinglive steam into the digester. The exact technique is not criticalprovided sufficient water is present with the green coffee under steampressure to produce treated coffee discharging from the vessel having amoisture content above 35 to 55 percent, preferably -50 percent waterbased on the weight of the wet beans. It has been found that when addinglive steam discharged coffee is above 35 percent, and preferably 40-50percent by weight water. While excellent results have been obtained atmoisture levels of 20-32 percent water, and at moisture levels of 45-55percent water, the best upgrading in green coffee flavor, as determinedafter roasting and brewing the coffee, is produced at a moisture levelafter treatment of 40-50 percent water on an as is basis. The properamount; of moisture and steam to be added in treating green coffee inorder to achieve a desired final moisture content can be readilyascertained via a few simple experiments.

It has been found that steam pressure treatment of a I mixture of waterand green coffee is most critical. The

amount of water absorption by the green coffee beans is highup to aboutequal parts of water added to the coffee. For example, increases of 15percent, 21 percent, and 26 percent on an absolute basis were observedin treating green beans moistened with an equal weight of water andtreated at pressures of 70, 90, and p.s.i., respectively for 5-minuteintervals, compared with green beans treated in a similar fashion butnot contacted with water. Increases in the amount of water added beyondan equal weight basis water to green coffee beans does not appreciablyfurther increase the quantity of water absorbed. Hence, higher levels ofwater addition result in only smaller increments of water absorption,while risking greater solids lost in residual water which is notabsorbed. For Robusta coffee, it has been determined that the optimumratio of water to green coffee beans is about 1:]; while with BrazilianParanas, the optimum water to coffee ratio is 0.5 parts water to onepart of coffee. Selection of the proper ratio for the particular varietyof bean is easily done with several experiments. The proper ratio isdetermined by the amount of water necessary under the conditions of timeand temperature selected for treatment to produce a moisture content inthe treated and flavor improved green bean of 4050 percent water.

Next to the addition of water, the next critical processing variable isthe steam pressure employed to treat the wetted green coffee. The steampressure selected regulates not only pressure but the temperature of theenvironment surrounding the green coffee, since saturated steam isnormally employed. Of course, wet steam or super-heated steam could beemployed with slight adjustment in the amount of water added to thegreen coffee, but saturated steam is preferred since it is readilyavailable. It has been found in following the prior art processes wherethe green coffee is not treated with water, that very little differencein the final moisture content of treated green coffee beans is observedwhen treated at 70, 90, and 125 p.s.i. steam. However, when a mixture ofone part green coffee and one part added water is treated, a 9 percentincremental increase in final moisture content is observed betweenprocessing at 70 and 90 p.s.i. Hence, while control of steam pressure inthe prior art process was not critical, it becomes so when prewet coffeeis to be treated. in treating prewet coffee, it has been found thatbelow a steam pressure of about 50 p.s.i., the upgrading effect oftreatment is insufficient to produce the desired characteristics in thefinal roasted and brewed coffee beverage. Also, at steam pressures ofabove 140 p.s.i. there has been found an undue downgrading in desirablecoffee characteristics, and again the flavor characteristics of thefinal beverage are not sufficiently improved. A steam pressure of 90p.s.i. for treating the wetted green coffee has been found mostdesirable and a preferred operating range is from 70l 10 p.s.i. steampressure.

The effect of residence time on the green coffee final moisture contentand flavor when treated with pressurized steam is not, apparently, ascritical as was the quantity of water added to the green coffee or thepressure of the steam employed in treating the green coffee. However, itis desirable to minimize the time of exposure of the green coffee tostream in the pressure vessel. At higher steam temperatures andpressures, the time period necessary to upgrade the coffee will be aminimum. Generally, in the process of this invention the beans aremaintained in the pressure vessel for l-l minutes, usually about 1-5minutes with a preferred treatment time of 2-4 minutes.

The temperature within the vessel is fixed by the type of steam employedand by heat losses which occur in the process. Ideally, the temperatureshould approach the temperature of saturated steam at the pressure beingmaintained within the vessel. Generally, in employing saturated steam,the temperature will normally be maintained at from 240-350 F within thepressure vessel, more particularly 3 l0-350 F.

The treated coffee after steam treatment is discharged through apressure lock, generally a rotary valve. The treated beans can be passedthrough the lock very rapidly as long as a sufficient period of time isallowed to vent off the vapors being discharged with the coffee beans,such that when the beans are finally discharged they are at or close toatmospheric pressure and do not, therefore, undergo substantial puffingor expansion. Some puffing is to be expected during the steam treatmentand on release to the atmosphere. This is because as water is taken intothe green coffee, a natural swelling occurs. We have found that infollowing the process of this invention, the treated green coffee whichhas been dried is normally up to 25 percent lighter than untreated drygreen coffee, although less than a 10 percent decrease in bulk densitydue to treatment is more typical. Therefore, there is apparently aslight irreversibility in that once the bean is expanded, it does notshrink completely to its original size after drying. However, quiteunexpectedly we have found that once the coffee is dried and then isroasted by conventional means, the steam treated dried and roasted wholecoffee has a bulk density of up to 30 percent heavier than untreatedroasted green beans with a 10-20 percent increase in bulk density moretypical.

It is possible directly after steam treatment to convey or otherwisetranpsort the treated green wet beans to conventional roasting equipmentand to roast the beans to the final desired roast color. However, wehave found it preferable to first air dry the treated green coffee to astable moisture content generally below 15 percent, and then toconventionally roast the dried, treated coffee. This procedure, inaddition to allowing greater flexibility of processing by allowingstorage of the treated green coffee prior to roasting, has the furtheradvantage that the drying apparently modifies the structure of the drygreen coffee such that less expansion than normal is obtained duringroasting. This results in a heavier bulk density and provides economiesin packaging the roasted coffee for sale. It further suggests economiesin soluble processing due to higher or heavier column loads duringpercolation.

Drying can be accomplished in any suitable dryer such as those employingheated air and generally those employing a drying method where varioustemperature zones of heated air are used. We have found that a dryingtemperature starting at about 250 F at the feed end of the dryer anddischarging at about 140 F is sufficient to produce a stable coffeehaving a moisture content averaging below 15 percent. It is important todesign the dryer so that the chaff normally present with green coffee,particularly after steam treatment, does not build up in the dryer. Thechaff problem can also be solved by removingthe chaff prior to dryingthe green coffee such as by passing the green coffee beans over avibrating screen and subjecting them to a water spray to wash away anychaff that is present.

Expert panel evaluation indicates that best flavor upgrading forlow-grade coffees characterized as having very strong, tarry, moldy,dirty, and earthy flavors is obtained from green coffee treated withfrom 0.25 to 1.5 parts water, preferably 0.4 to 1.2 parts water per onepart of green coffee by weight, at a steam pressure offrom 50 p.s.i. to140 p.s.i., preferably p.s.i. to l 10 p.s.i., and residence times in theorder of l-10 minutes, preferably about 5 minutes. Green coffee treatedunder these conditions is characterized as much cleaner in flavor thancontrol with only slight tarry and slight earthy notes. Most of thetarry character, as well as usually all of the moldy, swampy flavor isremoved. Water addition plays a significant role in removing theseundersirable flavors. Green coffee treated under the same pressuretreatment conditions with no water added, while slightly improved overthe original coffee flavor, still retains a high degree of the tarrycharacter and some moldy flavor notes present in the initial greencoffee. Thus, the process of this invention affords a significantfurther'improvement in the'art of steam treating green coffee.

While this process of upgrading is particularly applicable to Robustacoffee, the process has also been found to-up'grade other varieties suchas Arabica coffee from Brazil typified by Paranas, while removing someobjectionable flavors, the processing also appears to produce a moreMilds-type acid flavor from the Brazilian coffee.

While it is preferred to treat each variety of coffee separately so asto optimize process conditions of water addition, temperature, steampressure, and residence time, it is possible to treat blends. However, afurther advantage of processing each variety separately is that thetreated and usually dried variety can then be conventionally roasted toits optimum roast color and then blended with other roasted coffees toproduce the final blend for sale as regular coffee, or for furtherprocessing into'soluble coffee.

The process of this invention will' be further described with referencesto the following examples:

EXAMPLE I Green coffee comprising a blend of Robusta (lowcost Robustacoffees such as Madagascar, Camerouns, Undergrade Ugandas, Indonesians)and Undergrade Milds (such as Perus, Costa Ricas, Ecuadors) were placedin a jacketed autoclave and an equal amount of water was' added to theautoclave. The vessel was sealed and heat was appliedto vaporize thewater and increase the pressure within the autoclave to 90 p.s.i. Ittook approximately 3 minutes to raise the pressure within the vessel tothe desired point. Sufficient heat was maintained in the jacket of theautoclave to maintain the 90 p.s.i. pressure for a period of 3 minutes.The vapors were then vented out of the vessel over a period of 3 minutesto reduce the pressure within the vessel to almost atmospheric pressureand the green coffee was discharged from the autoclave. The coffee wasthen roasted by standard techniques.

The roasted coffee was roasted, ground, and percolated in a homepercolator and the resultant brew was found to be superior in flavor toa brew prepared from an equivalent blend of green coffee which was notsubjected to the upgrading treatment.

EXAMPLE II A blend of green coffee equivalent to that used in Example Iwas mixed with an equal amount by weight of water and fed through apressure lock into a continuous pressure digester which was at 90 p.s.i.pressure. Sufficient heat was applied to the jacket of the digester tovaporize the water introduced with the coffee. The coffee beans in thismanner were almost instantaneously exposed to the final pressure of 90p.s.i. The flights in the digester carried the beans from the inlet endto the discharge end in 3 minutes and the beans were then discharged viaa second rotary pressure look. In the discharge lock the beans werecarried in compartments and the pressure within a compartment wasreduced to atmospheric pressure before the beans were discharged to theatmosphere. By relieving the pressure while the beans were in a confinedzone, undue expansion of the beans was avoided. The green coffee wasthen roasted in a conventional manner and the roasted coffee was groundand percolated as in Example I. It was found that the flavorcharacteristics of the resultant brew were far superior to untreatedgreen coffee and showed a definite advantage over the coffee which hasbeen treated in the autoclave of Example I.

EXAMPLE III To a Bauer No. 459 M & D Digester designed to cookcellulosic materials is charged continuously 2,000 lbs. per hour ofgreen coffee. Traveling compartments formed by conveyor flightstransport the product within the digester through the steam pressureatmosphere. The digester is a cylindrical vessel closed at each end andinstalled at a 45 angle. The tank is divided along its axis into twosegments by a flat, hollow beam which may be used to indirectly heat thevessel s contents. The beam terminates before reaching each end of thecylinder. At the lower end of the cylinder there is an idler shaft,while at the upper end of the cylinder there is a drive shaft. Theseshafts form the end shafts of an endless flight conveyor driven by thetop shaft and maintained under tension by the lower shaft. The lowershaft is attached to a hemispherical head that forms the housing,similar in section to a segment of the vessel. The green coffee andwater to contact the coffee are introduced to a rotary valve fixed todischarge into the vessel 2,000 lbs. of coffee per hour. The greencoffee falls onto the flat, hollow beam where it is confined betweenconstantly moving flights of the conveyor. The flights carry the coffeedown the top side of the hollow beam around the lower end, and then upthe bottom half of the divided vessel to a discharge at the elevated endof the digester where the material is released through another rotaryvalve. When employing live steam for direct heating, the steam is addedthrough injectors into the digester. Their position is about two-thirdsof the way from the bottom of the digester to the inlet. Steam can alsobe added through the rotary feed valve to prevent buildup of loosecoffee particles. Temperature and pressure is easily controlled byregulating the inlet steam pressure, and the retention time within thedigester is controlled by regulating the speed of movement of theconveyor belt, and by controlling the rotation rate of the rotary valvesfeeding and discharging the digester. The water added with the greencoffee is generally absorbed by the coffee, and

while a small liquid head may be present in the lower portion of thedigester, it is preferred to minimize this in order to prevent solidsloss.

Two types of coffee-one Robusta from Madagascar and one BrazilianParanaswere individually treated in the previously described digester.Steam pressure was regulated at p.s.i. with percent water added to theMadagascar coffee and 50 percent water by weight of coffee added to theBrazilian coffee, as each was fed through the rotary valve. Each type ofcoffee was subjected to the 90 p.s.i. steam for an average residencetime of 5 minutes and was then discharged through the discharge rotaryvalve. On discharge, the average moisture content of the Madagascarcoffee was 48 percent water on a wet basis varying from 47-50 percent;and the average moisture content of the Brazilian coffee was 43.4percent water on a wet basis varying from 40.2 to 46 percent water. Thewet beans were passed over a Sweco vibrating screen and washed withwater to remove chaff and other small insoluble particles present withthe green bean. Each coffee was separately air dried to a stablemoisture content of below percent. During the run some of the addedwater and/or heating steam collected in the digester at an average of300 lbs. an hour was removed, representing 15 percent by weight of thebeans treated. Because the amount of condensate was minimized, thesolids removed with this condensate, averaging about 0.2 percent, wasnot appreciable. After drying, the green bean bulk density was measuredand was found from Madagascar to be 4 percent lighter at 39.7lbs./cu.ft. vs. 41.5 lbs./cu.ft. for untreated coffee; whereas theBrazilian was 7 percent lighter at 33.8 lbs./cu.ft. vs. 36.6 lbs./cu.ft.for untreated coffee. The dried coffee was separately roasted in aconventional Probat roaster to a roast color typical for these coffees,namely, 85 roast color for Madagascar and 60 roast color for theBrazilian coffee. The bulk density of the whole roasted bean wasunexpectedly found to be heavier than untreated roasted control forMadagascar, being 12 percent heavier at 28.8 lbs./cu.ft. vs. 25.7lbs./cu.ft.; and for the Brazilian percent heavier at 26.5 lbs./cu.ft.vs. 21.1 lbs./cu.ft. for untreated roasted control. For Madagascarcoffee it was found that roasted control. For Madagascar coffee it wasfound that at least 40 percent more of this type of coffee could beemployed in a blend without noticeable flavor difference.

Green coffee which has been upgraded by the process of this inventioncan be used to prepare improved coffee products in any of the knowncommercial processes. Thus, an improved soluble coffee as well asimproved vacuum packed coffees can be achieved by using the process ofthis invention to upgrade the quality of the green coffee. The termp.s.i. as used herein refers to pounds per inch gauge pressure.

The process of this invention is also useful as a cleaning method forgreen coffee beans prior to their roasting. The steaming process removesdirt and other noncoffee material from the surface of the green bean.The process also removes the silver skin or outer layer of the greencoffee bean. The process thus provides a green bean which when roastedis not contaminated with non-coffee materials and which further does notproduce the quantity of chaff conventionally produced during roasting.

The foregoing examples were for illustrative purposes only and the scopeof this invention is intended to be limited only by the appended claims.

We claim: 1. A process for upgrading green coffee comprising:contracting one part green coffee with 025-1 .5 parts water by weight toform a mixture;

subjecting the mixture in an enclosed pressure vessel to a steampressure maintained at 50 to 140 p.s.i. for from 1 to 10 minutes;

releasing the pressure and allowing the coffee to come to atmosphericpressure, thus depressurizing the coffee; and

roasting the coffee, said green coffee and water mixture containing anamount of water effective to produce a moisture content in thedepressurized coffee of above 35 percent to 55 percent by weight of thewet coffee.

2. The process of claim 1 where the amount of water is effective toproduce a moisture content of 45 to 55 percent by weight of the wetcoffee.

3. The process of claim 1 wherein one part green coffee is contactedwith 0.4-1.2 parts water and the mixture is subjected to a pressure ofto 1 l0 p.s.i.

4. The process of claim 3 wherein the coffee is retained in the vesselfor from about 1 to about 5 minutes.

5. The process of claim 1 wherein the vessel is a continuous pressurevessel wherein the coffee is conveyed from a feed end to a dischargeend, the coffee being introduced through a pressure lock at the feed endand discharged through a pressure lock at the discharge end.

6. The process of claim 5 wherein the coffee and water are mixedtogether in the pressure lock at the feed end of the vessel and rapidlyintroduced into the pressure vessel.

7. The process of claim 1 in which an external source of steam isemployed to directly contact the green coffee in the vessel.

8. The process of claim 1 wherein the steam pressure is produced byindirect heating of water present in the vessel sufficient to producethe steam pressure.

9. The process of claim 1 which further includes drying the steamedcoffee to a stable condition prior to roasting the coffee.

10. The process of claim 9 wherein the wet steamed green coffee is airdried to below 15 percent moisture. l

-UNITED STATES PATENTOFFICE CERTIFICATE 0Fv CORRECTION Patent m5.3,767,418 p g October 23, 1973 Inventofla) George B. Ponzoni et al It 19certified that error appears in the abbve-identified patent and thatsaid Letters Patent are hereby corrected 'as shown below:

In Column 1, Line 29 after FNo." end before "published" change...2,002,l89;.. to read ...2,022,l89...

Sigehd and sealed this 6th day of August 1974.-

(SEAL) 'Attest:

MCCOY M. GGIBSON, JR. c. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM PO-IOSO [10-69) U8COMM-DC 60378d=00 i 0.1. oovllulmlv nmmmonlcl In. o-au-su

2. The process of claim 1 where the amount of water is effective toproduce a moisture content of 45 to 55 percent by weight of the wetcoffee.
 3. The process of claim 1 wherein one part green coffee iscontacted with 0.4-1.2 parts water and the mixture is subjected to apressure of 70 to 110 p.s.i.
 4. The process of claim 3 wherein thecoffee is retained in the vessel for from about 1 to about 5 minutes. 5.The process of claim 1 wherein the vessel is a continuous pressurevessel wherein the coffee is conveyed from a feed end to a dischargeend, the coffee being introduced through a pressure lock at the feed endand discharged through a pressure lock at the discharge end.
 6. Theprocess of claim 5 wherein the coffee and water are mixed together inthe pressure lock at the feed end of the vessel and rapidly introducedinto the pressure vessel.
 7. The process of claim 1 in which an externalsource of steam is employed to directly contact the green coffee in thevessel.
 8. The process of claim 1 wherein the steam pressure is producedby indirect heating of water present in the vessel sufficient to producethe steam pressure.
 9. The process of claim 1 which further includesdrying the steamed coffee to a stable condition prior to roasting thecoffee.
 10. The process of claim 9 wherein the wet steamed green coffeeis air dried to below 15 percent moisture.